fix(SD): add a display timer on status page

[pluce]

Fixes #8046

Summary of Changes

The Status Page page of lower ECAM / System Display should appear only 3s if no failures are to be shown. This PR adds this timer before coming back to previous page.
Also replaces hardcoded values by constants to improve readability in the PageContainer component.

References

FCOM (page 1190)

Additional context

First PR 👀

Testing instructions

Should not change behaviour of lower ECAM beside returning to previous page after 3s if no failure. I couldn't make Status page to be filled by anything, but after a discussion on Discord it may be normal.

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[pluce]

• Change the constants list for pages to an Enum

[2hwk]

Lint is failing, please fix
https://github.com/flybywiresim/a32nx/actions/runs/5125901688/jobs/9223580234?pr=8048

[pluce]

should be good @2hwk thanks !

[Mack674]

Quality Assurance Tester Report

Discord: Mack674#2274
Object of testing: #8048
Tier of Testing: 1
Date: 30/06/2023

Testing Process:

• Spawned C&D at the gate
• Turned on Batteries 1&2 and external power
• Checked behaviour of STS ecam page

Negatives: N/A

Testing Results: Passed

Conclusions: Works as intended. Great job!

Media:

Microsoft.Flight.Simulator.2023-06-30.17-33-47.mp4